The present invention relates to improvements in the manufacture of helical coils, and, in one particular aspect, to novel and improved apparatus for the reliable automated manufacture of helical anchor-bolt coils from pre-cut flat metal blanks. Such coils are useful as elements of expansion-type fasteners, or anchor bolts, like those of my U.S. Pat. No. 3,881,393, dated May 6, 1975.
Helical coils are commonly produced from continuous stock, whereby a sustained hold or grip and control of the material can readily be maintained until each desired helix is fashioned and cut off as a separate coil. In some instances, however, it is a handicap that the cross-section of continuous stock cannot conveniently be a variable one, and the designer and manufacture must accept that limitation unless willing to resort to hand-worked shaped blanks and non-automatic coil forming. Stock in the form of separate flat pieces, or blanks, presents a classic production dilemma, because of problems associated with handling, conveying, gripping and feeding such parts during processing. In the case of blanks suitable for formation of coils used in expansion fasteners according to my said U.S. Pat. No. 3,881,393, the individual flat sheet-metal pieces of stock are tapered in width and have no flanges, perforations or other features which might assist in their handling; however, such blanks are nevertheless processed automatically into closely-controlled helical coil form in accordance with the practices disclosed herein and with the aid of apparatus constructed according to the present teachings.